The present invention relates to an intermittent type swirl injection nozzle for an internal combustion engine capable of providing a desired angle of spray divergence, penetration (reach) of the spray, and fuel atomization by providing both swirling and straight flows in fuel flow passages through an injection nozzle. The invention further relates to such an injection nozzle in which the flows can be controlled in swirling and straight directions.
In stratified charge engines and Diesel engines wherein fuel is injected into combustion chambers of the engine, the fuel injection system has had to meet increasingly stringent requirements of combustion efficiency and performance. To achieve the best performance of an engine over a wide range of operating conditions relative to engine speed and loads, there is required a fuel injection system which is adaptable for all operating conditions.
A fuel injection system for a Diesel engine includes as primary components a fuel pump, connecting pipes and fuel injection nozzles. Of these, it is well known that the spray characteristics of the fuel injection nozzle particularly strongly affects the performance of the engine. The atomized fuel discharged from the fuel injection system into the combustion chamber can be made to form an optimum fuel-air mixture provided that the particle size of the spray, the angle of divergence (spray angle), the penetration of the spray, the required fuel quantity for each injection, and the like are properly determined in accordance with the flow rate of the air taken into the combustion chamber. Moreover, adaptation of injection timing, injection period and coefficient of intake air utilization are important to improve the thermal efficiency of the engine and to suppress the generation of smoke.
In order to satisfy the requirements above, it has been attempted to increase the injection pressure of the fuel, make the diameter of the nozzle hole as small as possible, and provide a plurality of nozzle holes. Moreover, attempts have been taken to redesign the shapes of the pintle and the throttle valve and implement the valve lift control, including adopting a plurality of injection nozzles. However, with the use of conventional swirl type injection nozzles, it is not always possible to ensure satisfactory fuel atomization, the desired angle of spray divergence, and the desired penetration of fuel particles. In addition, such a conventional injection nozzle is complicated in construction and is expensive.